On February 24, 1981, Prince Charles announced his engagement to Lady Diana Spencer.
In official photos, the supposedly happy couple posed with his mother the Queen.
While for Lady Diana this was her official introduction to the world, the 19-year-old had known Her Majesty her entire life.
The dynamic between Diana and the Queen was certainly a complicated one and stretched back to when Diana was born in Park House – a rented house on the Queen's Sandringham estate.
As a child, she would be brought to play at the "big house" with the young Princes Andrew and Edward.
Initially, the Queen thought the pairing of Charles and Lady Diana, the shy blonde aristocrat, was "inspired," according to the Daily Mail's Richard Kay (who had been a friend of Diana).
However, things became complicated in the lead-up to the wedding when the teenage bride-to-be moved into Buckingham Palace and found her temporary home a confounding and cold place.
The Queen, royal biographer Ingrid Seward has reported, assumed that Diana would have no trouble fitting in, writing to a friend in March 1981, "I trust that Diana will find living here less of a burden than is expected."
Despite initial optimism, Diana's realisation of Charles' continued affections for Camilla Parker Bowles and the rigidity and frostiness of life inside the palace saw her mental health suffer.
According to Kay, the Queen took Diana riding several times at Sandringham in an attempt to bond with her new daughter-in-law, however the new Princess of Wales' fear of riding soon put paid to that.
Tensions were further strained between Her Majesty and Diana as the younger royal's star soon eclipsed the rest of the royal family's.
When the two women arrived at a polo match together and the waiting press started snapping, the Queen is reported to have commented, "I suppose I had better get out of the way."
As the Wales' marriage disintegrated in the '80s, the chasm between Diana and her husband's family grew.
In a letter penned by Diana in 1991 she wrote, "I do feel extremely isolated more than ever now, as I see what's coming to this country and this family," and that, "I am continuously misunderstood by those around me."
Still, Diana turned to the Queen for both solace and advice. One of the Queen's staff told Seward that Diana would pop around to Buckingham Palace for unscheduled visits. She quotes a footman saying after one such visit: "The Princess cried three times in a half an hour while she was waiting to see you." To which the Queen responded: "I had her for an hour – and she cried non-stop."
Andrew Morton, who collaborated with the Princess on the 1992 tell-all Diana: Her True Story wrote that "behind the public smiles and glamorous image was a lonely and unhappy young woman" and that she was seen "as an outsider by the Queen".
A friend of the Queen's told Kay that "she felt the pretty girl was a misfit who didn't quite contribute to the things they did and what they wanted her to do in the family.
"There was no real compatibility. Initially she was sympathetic, but later on I don't think she felt sorry for her, not really."
That disconnect extended to the causes the passionate young Princess wanted to focus on. According to reports, when Diana told the Queen she wanted to "get involved" with Aids, the monarch responded tepidly saying, "Can't you do something nice?"
It was the publication of Morton's bombshell biography in 1992, which detailed Diana's eating disorder and suicide attempts for the first time, that undid the remaining sympathy the Queen had for the superstar royal.
"The Queen was stunned," biographer Seward has written. "She was well aware how unhappy her daughter-in-law was, but never imagined Diana would air dirty linen in such a way."
In December that year, Prime Minister John Major informed the UK Parliament that Charles and Diana were separating.
Diana would still visit the Queen and would, according to Kay, weep as she told Her Majesty that "everyone was against her".
"The Queen didn't know what to do. She has always hated this kind of emotional confrontation and, frankly, has never had to deal with it before or since," a lady-in-waiting said.
In 1995, after Diana sat down with the BBC's Newsnight programme and coyly told interviewer Martin Bashir, "There were three of us in the marriage," the Queen made the decision that it was time for Charles and Diana to divorce. Her Majesty wrote to both of them, starting her missive to the Princess writing, "Dearest Diana." It was signed, "With love from Mama."
In 1996, their divorce was finalised and the Princess emerged as a global power player, advocating for the end of landmines and travelling to Bosnia and Angola.
Then in the early hours of August 31, 1997, the relaxing summer reverie that the Queen, Prince Charles and Princes William and Harry had been enjoying at Balmoral was shattered when news broke of Diana's death in a Paris tunnel.
In the hours and days afterwards, Her Majesty faced a nation grief-stricken and deeply aggrieved by what they perceived as her cold-hearted handling of the situation as she refused to return to London or fly the flag at half mast at Buckingham Palace. (Her rationale was that she wanted to stay with her devastated grandsons and that the flag is only raised and lowered when the sovereign is in residence.)
Finally, she went south to London and made only the second TV address of her reign (aside from her annual Christmas speech). Wearing black and appearing on screens around the world live, the Queen said of Diana: "She was an exceptional and gifted human being. In good times and bad, she never lost her capacity to smile and laugh, nor to inspire others with her warmth and kindness.
"I admired and respected her – for her energy and commitment to others, and especially for her devotion to her two boys."
Matariki celebrations will be taking place across the country throughout the weekend.